Energy-absorbing steering column

ABSTRACT

An automotive vehicle energy-absorbing steering column assembly includes an energy-absorbing support jacket comprised of upper and lower telescopic sections having interposed therebetween a ball-type energy-absorbing deformer structure providing a first level of energy absorption for an initial amount of forward displacement of the steering wheel whereafter the upper section abuts a third section telescopically mounted on the lower section with a further ball-type structure therebetween so that continued displacement of the steering wheel forwardly of the vehicle is met with a second higher level of energy absorption.

United States Patent I I I I Inventors Robert C. Farrell:

John W. Shelley, both at Saginaw, Mich. 88l,l90

Dec. l, I969 July 6, I971 General Motors Corporation Detroit. Mlch.

Appl. No Filed Patented Assignee ENERGY-ABSORBING STEERING COLUMN 9Claims, 4 Drawing Figs.

74/492 lnt.Cl. 3620! ll]! Field olSelrch 74/492, 493

Relennces Cited UNITED STATES PATENTS 7/1969 Toshida et al7 3,461,7408/1969 Tajimaelal. i.

Primary Examiner- -Milton Kaufman Attorneys-W. E. Finlten and D. L.Ellis ABSTRACT: An automotive vehicle energy-absorbing steering columnassembly includes an energy-absorbing support jacket comprised of upperand lower telescopic sections having interposed therebetween a ball-typeenergy-absorbing deformer structure providing a first level of energyabsorption for an initial amount of forward displacement of the steeringwheel whereafter the upper section abuts a third section telescopicallymounted on the lower section with a further balltype structuretherebetween so that continued displacement of the steering wheelforwardly of the vehicle is met with a second higher level of energyabsorption.

ENERGY-ABSORBING STEERING COLUMN This invention relates to energyabsorption constructions and more particularly to energy-absorbingsteering column assemblies for automotive vehicles.

This invention is directed to providing improvements forenergy-absorbing steering columns in respect of et'ficiently controllingthe level of energy absorption at a uniform level during the fullexcursion of collapsing movement within the column under forces appliedto the vehicle steering wheel. The kinetics of such columns, includingthe structural inertia of and friction between the various parts thereofas well as the effect of breakaway shear-type structures holding normalrelation in the column may give rise to an initial very brief peak load,whereafter during collapse the loading falls off to a lower value withconsequent lower level of energy absorption therein. it is desirable toreduce the difference between such loadings in the time history ofcollapse while achieving maximum energy absorption, but not exceeding anominal maximum load to be sustained in the column assembly. It issometimes also desirable, for other reasons than the elimination of aninitial peak load, to have the capability of gradually or otherwiseincreasing the load level in the column during the time history ofcollapse from an initial low level to a final higher level of load.

It is accordingly the primary object of this invention to provideenergy-absorbing construction for steering columns and the like whereinthe time history of column displacement or collapse includes a firststage or level of load at the completion of which there is met adifferent higher level of load.

Another object of the invention is to provide energy-absorbingconstruction for steering columns and the like wherein a first energyabsorber unit is operative in an initial stage of column loading underforces applied to the vehicle steering wheel to provide a first reducedlevel of energy absorption, which may be controlled to be of relativelyshort duration corresponding only with what would otherwise be a normalperiod of peak loading, whereafter continued column displacement is metwith an increased level of energy absorption arising from the operationof a second energy absorbing unit.

A further object of the invention is to construct an energyabsorbingsteering column support jacket or like energy-absorbing structure withtelescopically related sections including first and second energyabsorber units operative sequentially during initial and later stages ofcolumn collapse to provide a predetermined time history of energyabsorption during the full telescoping excursion thereof.

A further object of the invention is to incorporate within such anenergy-absorbing structure a first energy absorber unit comprised ofball-type deformer rolling bodies operative during an initial stage ofdisplacement between telescoping portions of the construction whereafterabutment means between such portions engage to bring into operationduring continued such displacement a second energy-absorbing unit suchas a further unit of ball-type deformer bodies, a corrugated tubesection subject to accordionlike collapse, or other energy-absorbingunit.

Yet another object of the invention is to provide energy-absorbingsteering column apparatus including an energyabsorbing support jacketconstructed of upper and lower telescopically related jacket sectionsinterengaged by a deformer ball-type of energy-absorbing unit operativeduring an initial stage of downward telescoping of the upper sectionunder forces applied to the vehicle steering wheel to provide a firstreduced level of energy absorption during a predetermined amount of suchdisplacement, whereafter the upper section engages througi an abutmentconformation thereon with a further telescopically related tube andball-type energy-absorbing deformer unit on the lower section so thatthe upper section and further tube telescope as a unit over the lowersection and the two energy-absorbing units operate conjointly to providean increased level of column loading and energy absorption over theremainder of the collapse or energy-absorbing excursion of the column.

These and other objects, features and advantages of the invention willbe readily apparent from the following specification and from thedrawings wherein:

FIG. 1 is a fragmentary partially broken-away elevational view of anautomotive vehicle body including steering column apparatusincorporating energy-absorbing construction according to this invention;

FIG. 2 is an enlarged partially broken-away view taken generally alongthe plane indicated by lines 2-2 of FIG. 1;

FIG. 3 is a sectional view taken generally along the plane indicated bylines 3-3 of FIG. 2; and

FIG. 4 is a view similar to FIG. 2 showing a modified form of theinvention.

Referring now particularly to FIG. 1 of the drawings, anenergy-absorbing construction according to the present invention isspecifically disclosed for vehicle passenger injury protection in anautomotive vehicle body designated generally as 10, including a steeringcolumn assembly l2 extending from the vehicle steering gear, not shown,at its one end to within the vehicle passenger compartment to mount atits other end a steering wheel 14.

As best shown in FIG. 2, a steering shaft 16 for operatively connectingthe steering wheel 14 with the steering gear includes a pair oftelescopically and nonrotatably related sections 18 and 20 adapted uponthe application thereto of sufficient axial thrust to telescope in thedirection of the applied thrust. The sections 18 and 20 are releasablyheld in the normal operating relation shown by a plurality ofinjectionmolded plastic shearpins 22 subject to fracture underpredetermined axial load on the sections. The steering shaft [6 isgenerally conventionally rotatably supported for normal operation of thevehicle steering gear by a surrounding generally tubular support jacketassembly 24 incorporating the energy-absorbing construction of thepresent invention.

Such jacket assembly basically includes a pair of upper and lowertelescopically related cylindrical jacket sections 26 and 28. By meansto be described, such sections are joined rigidly to provide for firmassociation for proper support of the steering shaft within the vehicleyet are subject to controlled collapse and absorption of the energy offorces applied to either the steering wheel 14 or to the lower end ofthe steering column.

Adjacent the steering wheel 14, section 26 is releasably held on avertical wall portion 30 of the conventional vehicle instrument panelstructure by a one-way shearable bracket assembly including a generallyU-shaped bracket member 32 welded or otherwise fixed to section 26. Thebracket member is provided with open-ended slots 34 receiving therein apair of mounting capsules 36 having pairs of side flanges embracing thebracket and releasably secured thereto by a series of plastic shearpins38 in situ injection molded between such flanges and the bracket. Hangerbolts 40 depend from the vehicle cowl structure and project throughapertures in capsule 36 to receive nuts bearing on the underside of thecapsules and threadably operative to firmly support the bracket andsteering column support jacket 24 in the vehicle. Upon the applicationof forward axial thrust to section 26 under forces applied to steeringwheel 14 sufficient to shear the pins 38, the bracket member may moveforwardly out of the cap sules for release of the section from theinstrument panel. Upon rearward axial thrust from section 26 however,there is met the reaction of bolts 40 which prevent rearwarddisplacement of the section from the instrument panel.

Section 28 is fixedly secured to the firewall structure 42 of body 10 byan anchorplate assembly 44 operative to prevent movement of such sectionin either axial direction under forces applied thereto from the steeringgear or from the steering wheel 14.

Structurally associated with the wall portion 30 and bolts 40 is one endportion of the usual pedal support bracket 46 which extends downwardlyfrom welded or like attachment to the vehicle cowl structure to assistin the structural support of the steering column as well as to mount thevarious vehicle control pedals including a clutch pedal 48 at one sideof the column, and the brake pedal 50 at the other side thereof. Suchbracket includes a forward bracket portion 52 for a purpose later toappear.

With particular reference to FIG. 2, support jacket sections 26 and 28are firmly joined by an energy-absorbing unit which may be generallycharacterized as a ball-type deformer and energy-absorbing structuredesignated generally as 54. Such unit corresponds identically with thedisclosure of the US. Pat. to White No. 3,392,599 issued July 16, l968and assigned to the assignee of the present invention. Reference may behad to that patent for a detailed discussion of the characteristics andstructure of unit 54 but generally the same comprises a plurality ofdeformer balls arranged in at least two axially spaced annular rows 56and 58, each of such balls being rollably held captive in a circularaperture provided in a plastic or like sleeve 60 disposed between thejacket sections. Balls 56 and 58 are received between the walls of thesections with a predetermined interference fit and are of such anelevated value of material hardness relative to the material hardness ofeither or both sections 26 and 28 as to be operative to roll over thewalls thereof during forced telescoping movement of the sections as aresult of the application of axial force thereto from either thesteering gear or the steering wheel 14. As the balls 56 and 58 roll as aunit with sleeve 60 during such telescoping, the balls causepredetermined amounts of energy absorption arising from the localizedplastic strain deformation or grooving caused in the walls of thesections.

Referring also to FIG. 3, there is received over section 28 in spacedrelation below section 26 a further cylindrical member 62. Providedagain between this member and section 28, is a further or secondenergy-absorbing unit. in the present embodiment, this unit againcomprises a ball-type deformer and energy-absorbing constructionidentical in most respects to that just described for energy-absorbingunit 54. The second unit, designated generally as 64, comprises twoaxially spaced rows 66 and 68 of deformer balls again placed withinterference fit between section 28 and member 62 and received withinindividual apertures of a sleeve 70. When mounted in the vehicle body10, the member 62 and energy-absorbing unit 64 are disposed in relationto bracket portion 52 so that a restraining arm 72, extending downwardlyfrom the bracket portion, mounts a restraining pawl 74 of strong plasticor like construction having a beveled end 76 thereof received withinaperture 78 of member 62 and a similar aperture 80 in the sleeve 70.

Energy absorber units 54 and 64 are constructed to provide differentlevels of energy absorption or load-creating resistance to telescopingmovement within support jacket 24. Specifically, energy-absorbing unit54 is constructed to impart a predetermined level of load and energyabsorption between sections 26 and 28, while energy absorber unit 64provides predeterminately higher level of energy absorption betweenmember 62 and section 28. This is conveniently done within the teachingsof the White patent by a number of methods, but preferably it is done byplacing the balls 56 and 58 with a predetermined interference fitbetween its mating members and by disposing balls 66 and 68 with apredeterminately higher interference fit between its mating members.

It will be noted that there is an axial gap between the lower end ofsection 26 and the upper end of member 62. Flanges 82 and 84 areprovided thereon to form an abutment means for a purpose now to bedescribed. In operation, and assuming first a downwardly applied forceon steering wheel 14 sufficient to cause shearing of the various shearstructures and telescoping of steering shah l6 and column collapse andenergy absorption within unit 54, initial downward displacement ofsection 26 telescopically over the firewall-held section 28 causes balls56 and $8 to impart energy absorption by plastic deformation in thesetwo sections. This occurs to provide a first lower level of loading insteering column 12 selected at a value as to provide for an acceptableloading at the steering wheel 14 during the initial stage or portion ofthe collapse time history, which may involve additive loadings frominitial resistance to fracture of shearpins 22, initial frictionalresistance in the telescoping and breakaway parts, etc. At thecompletion of this initial stage, section 26 has telescoped over section28 the distance provided between flanges 82 and 84 whereupon suchflanges engage and abut the downwardly displacing section 26 with member62. At this point, continued downward telescoping of section 26 carrieswith it the member 62 thereby bringing into operation the secondenergy-absorbing unit 64.

The load-creating resistance and energy absorption provided by theadditional unit 64 then creates an additive con tribution to thatimposed by unit 54; i.e., all four rows of balls 56, 58, 66 and 68 areoperative to roll and provide plastic strain grooving in the walls ofsection 26 and member 62 as the latter telescope over section 28, whichalso receives grooves. It will thus be appreciated that a second orhigher level of energy absorption may be provided for the remainder ofthe time history of collapse in the column following the engagement ofthe abutment flanges 82 and 84. Thus, having accomplished an initiallower value of energy absorption in unit 54 to avoid a high-peak load, alater higher load may obtain in the column from the contribution of bothunits to achieve maximum energy absorption through the greatest portionof displacement, or any portion thereof which is desired by properselection of the spacing of member 62.

The various members in the support jacket assembly may be assembled byfirst disposing member 62 and energy absorber unit 64 on the upper endof section 28 and, with the use of a guide fixture, forcibly telescopingthe subassembly of the member 62 and unit 64 in fixed relationdownwardly over the section 28 to the position shown. The assemblyoperation will impart a plurality of grooves in the outer wall ofsection 28 while the energy absorber unit 64 is held in fixed relationin member 62, thereby occasioning an extent of localized plasticdeformation in the inner wall of such member. However, during thecollapse sequence above described, the unit 64 of balls 66 and 68 areoperative to efficiently further roll over the wall of section 28 aswell as over the wall of member 62 until it enters section 26 to deformits wall. lt is of course to be appreciated that the various balls 56,S8, 66 and 68 are rotatably misaligned around section 28 in a staggeredrelation so that no two balls travel axially thereon in the same path.It will be appreciated that during the collapse sequence abovedescribed, the two energy absorber units 54 and 64 once having movedcloser together to the point of abutment of flanges 82 and 84,thereafter remain in fixed spaced relation axially of section 28 and donot interfere with each other during the later final stage of collapseto alter operation.

During the described collapsed sequence, the pickup of member 62 bysection 26 to occasion conjoint telescoping thereof is not resisted bypawl 74 since a cam edge 86 of aperture 78 engages the cam-shaped end 76of the pawl to force it resiliently upwardly out of aperture 78 and 80thereby permitting mu telescoping collapse within the support jacket.However, pawl 74 is preferably arranged as shown to hold member 62 andenergy absorber unit 64 against upward movement during the opposite typeof column displacement occasioned by displacement of the vehiclesteering gear and deformation of the firewall 42. In these conditions,section 26 is of course held stationary through reaction of supportbracket 32 and the rearward displacement of section 28 is operative tocause energy absorption in energy absorption unit 54 similar to thatjust described for forward collapse. So that any subsequent forwardcollapse occasioned by forces on steering wheel 14 may meet with thesuccessive different levels of energy absorption described above, thepawl 74 operates during the rearward collapse to hold member 62 and unit64 in the relationship shown wherein flanges 82 and 84 are held spacedapart. Thus, the end 76 of the pawl engages the lower ends of apertures78 and 80 to hold these parts and ac cordingly the balls 66 and 68merely skid over the section 28.

This skidding also provides increased resistance to the rearwarddisplacement of section 28.

In FIG. 4, there is shown a modification of the present inventionwherein the support jacket designated generally as 24' again includesupper and lower sections 26' and 28' such as in the first embodiment butdiffering therefrom in respect of the interchange of smaller and largerdiameters between upper and lower sections. Again, an energy absorberunit 54' may be interposed between these sections to provide a firstreduced level of energy absorption during initial telescoping movementbetween the sections. Rather than having the releasable bracket assemblyfixed to the upper section, such a bracket assembly 32' is welded to thelower section 28'.

The second absorber unit comprises an annularly corrugatedenergy-absorbing integral structural portion 88 of section 28'constructed of a meshlike network of interconnected strip elementssimilar to that disclosed in US. Pat. to Wight et al. No. 3,373,629issued Mar. [9, i968. An abutment collar 90 is welded or otherwise fixedto upper section 26' in assembled spaced relation to the upper portionof section 28'. As indicated in the first embodiment, energy-absorbingunit 54' may be constructed to provide a predetermined level of energyabsorption and load imposition during initial collapse, whereafter, inthis embodiment, the energy-absorbing portion 88 takes over completelyto individually provide a higher level of energy absorption at a valueselected by use of the structural expedients of material, stockthickness, etc., described in the Wight et al. patent.

In operation, downward telescoping movement arising from forces appliedto the steering wheel I initially causes energyabsorbing unit 54 tocause plastic strain grooving in the upper section 26' and in the upperportion of section 28 at the selected level of load until the flange ofabutment collar 90 engages the end of section 28. At this point, the twosections are abutted against further relative movement therebetweenthereby eliminating operation of unit 54' so that the downwardly appliedloads are transferred directly to energyabsorbing portion 88 for energyabsorption therein at the selected higher level.

in a rearward collapse of the column with rearward displacement offirewall 42, the reaction at bracket 32 dictates that all energyabsorption will arise from crushing of energy absorbing portion 88 ofsection 28'.

It is to be appreciated that various structural alternatives areavailable for substitution in place of the specific deformer unitswithin the herein disclosed concept of successively operating the twoenergy-absorbing units, either alone or in combination in the finalstage of collapse. Further, it will be apparent that the initial forceloadings in the energy-absorbing construction may be selected to be of ahigher value than that of the second stage of collapse rather thanlower. It will also be appreciated that the specific arrangement of thetelescoping parts of support jacket 24 or any similar energy absorbermay be altered from the embodiments shown by reversal of inner and outerparts and corresponding changes in the abutment flanges therebetween.

Having specifically described two illustrative embodiments of theinvention, what I claim as the invention is:

l. in energy-absorbing steering column apparatus for automotive vehiclesincluding a telescopic steering shaft adapted for operative connectionbetween the steering gear of the vehicle and a manual steeringinstrumentality, and support jacket means mountable on the vehicle androtatably supporting said shaft, the improvement comprising, said jacketmeans being constructed of telescopically related upper and lowermembers, the upper of said members being adapted to telescope relativeto the lower of said members upon forces being applied to saidinstrumentality downwardly toward said lower section, firstenergy-absorbing means in said jacket means and operative during aninitial stage of said downward telescoping movement between said membersto provide a first level of controlled resistance thereto, secondenergy-absorbing means carried by said jacket means, and abutment meansengageable upon completion of said first stage of downward telescopingmovement to connect said upper member in force-transferring relationwith said second energy-absorbing means such that the latter isresponsive to continued downwardly applied forces on said manualinstrumentality to provide a second level of controlled resistance todownward displacement of said upper member following said first stage ofmovement thereof.

2. The improvement recited in claim 1 wherein said abutment means areengsgeable to connect said upper member in force-transferring relationthrough both said first and second energy-absorbing means so that boththereof contribute to said second level of resistance.

3. In energy-absorbing steering column apparatus for automotive vehiclesand including a telescopic steering shaft adapted for operativeconnection between the steering gear of the vehicle and a manualsteering instrumentality, and a support jacket means mountable on thevehicle and rotatably supporting said shaft, the improvement comprising,said jacket means being constructed of telescopically related upper andlower members, the upper of said members being adapted to telescoperelative to the lower of said members upon forces being applied to saidinstrumentality downwardly toward said lower member, spaced annular rowsof deformer rolling bodies interposed with interference fit between saidmembers operative to roll thereover during an initial stage of saiddownward telescoping movement between said members and to effectpredetermined plastic strain grooving therein during such movement toprovide a first level of controlled resistance thereto, a secondenergy-absorbing means carried by said jacket means, and abutment meansengageable upon completion of said first stage of downward telescopingmovement to connect said upper member in force-transferring relationwith said second energy-absorbing means such that the latter isresponsive to continued downwardly applied force on said manualinstrumentality to provide a second level of controlled resistance todownward displacement of said upper member following said first stage ofmovement thereof.

4. The improvement recited in claim 3 wherein said abutment means areengageable to connect said upper member in force-transferring relationthrough both said first and second energy-absorbing means so that boththereof contribute to said second level of resistance.

5. The improvement recited in claim 3 wherein said secondenergy-absorbing means comprises a portion of said lower memberconstructed in annularly corrugated manner to be subject toaccordionlike radial expansion and axial shortening under said forces,said abutment means being adapted to connect said upper member directlywith said lower member.

6. The improvement recited in claim 3 wherein said secondenergy-absorbing means comprises a second set of spaced annular rows ofdeformer rolling bodies interposed with interference fit between saidlower member and a further member received over said lower member, saidabutment means being adapted to connect said upper member with saidfurther member for conjoint telescoping movement thereof relative tosaid lower member following said first stage of movement.

7. The improvement recited in claim 1 further including one-wayreleasable bracket means fixed to said upper member and adapted forattachment within the vehicle in a manner permitting said downwardtelescoping movement thereof but preventing upward movement thereof, atleast one of said energy-absorbing means being operative for controlledresistance to upward movement of said lower member against the reactionprovided by said bracket means.

8. An energy absorber comprising first tube means, second tube meanstelescopically related with said first tube means, at least one annularrow of deformer rolling bodies interposed with interference fit betweensaid first and second tube means and operative to roll thereover duringan initial stage of telescoping movement between said tube means in onedirection to effect predetermined plastic strain grooving therein duringsuch movement providing a first level of energy absorption, third tubemeans telescopically related with said second tube means, at least oneannular row of deformer rolling bodies interposed with interference fitbetween said second and third tube means operative to roll thereover during telescoping movement therebetween to effect predetermined plasticstrain grooving therein, and abutment means on said first and said thirdtube means engageable following completion of said first stage oftelescoping movement of said first tube means to connect said first andthird tube means for conjoint telescoping movement relative to saidsecond tube means and conjoint rolling of the first and the lastmentioned rows of deformer bodies so that continued telescoping movementof said first tube means in said one direction occurs with a secondlevel of energy absorption effected by both said first and lastmentioned rows of deformer bodies.

9. In energy-absorbing steering column apparatus for automotive vehiclesand including a telescopic steering shaft adapted for operativeconnection between the steering gear of the vehicle and a manualsteering instrumentality, and a support jacket mountable on the vehicleand rotatably supporting said shaft, the improvement comprising, saidjacket being constructed of telescopically related upper and lowertubes, the upper of said tubes being adapted to telescope relative tothe lower thereof upon forces being applied to said instrumentalitydownwardly toward said lower tube, one-way releasable bracket meansfixed to said upper tube and adapted to permit said downward telescopingmovement thereof but prevent upward movement thereof, at least twoaxially spaced annular rows of deformer balls interposed withinterference fit between said tubes and operative to roll thereoverduring an initial stage of said downward telescoping movement of saidupper tube to effect predetermined plastic strain grooving in said tubesproviding a first level of controlled resistance to such telescopingmovement, a third tube received telescopically over said lower tubebelow said upper tube, at least two axially spaced annular rows ofdeformer balls interposed with interference fit between said lower andthird tubes operative to roll thereover during telescoping movementtherebetween to effect predetermined plastic strain grooving therein,and abutment flanges means on said upper and said third tubes engageableupon completion of said first stage of downward telescoping movement ofsaid upper tube to connect said upper and third tubes for conjointtelescoping movement downwardly relative to said second tube such thatboth the first and the last mentioned spaced rows of deformer balls areresponsive to such continued downward telescoping movement to provide asecond higher level of controlled resistance to such movement.

1. In energy-absorbing steering column apparatus for automotive vehiclesincluding a telescopic steering shaft adapted for operative connectionbetween the steering gear of the vehicle and a manual steeringinstrumentality, and support jacket means mountable on the vehicle androtatably supporting said shaft, the improvement comprising, said jacketmeans being constructed of telescopically related upper and lowermembers, the upper of said members being adapted to telescope relativeto the lower of said members upon forces being applied to saidinstrumentality downwardly toward said lower section, firstenergy-absorbing means in said jacket means and operative during aninitial stage of said downward telescoping movement between said membersto provide a first level of controlled resistance thereto, secondenergy-absorbing means carried by said jacket means, and abutment meansengageable upon completion of said first stage of downward telescopingmovement to connect said upper member in forcetransferring relation withsaid second energy-absorbing means such that the latter is responsive tocontinued downwardly applied forces on said manual instrumentality toprovide a second level of controlled resistance to downward displacementof said upper member following said first stage of movement thereof. 2.The improvement recited in claim 1 wherein said abutment means areengageable to connect said upper member in force-transferring relationthrough both said first and second energy-absorbing means so that boththereof contribute to said second level of resistance.
 3. Inenergy-absorbing steering column apparatus for automotive vehicles andincluding a telescopic steering shaft adapted for operative connectionbetween the steering gear of the vehicle and a manual steeringinstrumentality, and a support jacket means mountable on the vehicle androtatably supporting said shaft, the improvement comprising, said jacketmeans being constructed of telescopically related upper and lowermembers, the upper of said members being adapted to telescope relativeto the lower of said members upon forces being applied to saidinstrumentality downwardly toward said lower member, spaced annular rowsof deformer rolling bodies interposed with interference fit between saidmembers operative to roll thereover during an initial stage of saiddownward telescoping movement between said members and to effectpredetermined plastic strain grooving therein during such movement toprovide a first level of controlled resistance thereto, a secondenergy-aBsorbing means carried by said jacket means, and abutment meansengageable upon completion of said first stage of downward telescopingmovement to connect said upper member in force-transferring relationwith said second energy-absorbing means such that the latter isresponsive to continued downwardly applied force on said manualinstrumentality to provide a second level of controlled resistance todownward displacement of said upper member following said first stage ofmovement thereof.
 4. The improvement recited in claim 3 wherein saidabutment means are engageable to connect said upper member inforce-transferring relation through both said first and secondenergy-absorbing means so that both thereof contribute to said secondlevel of resistance.
 5. The improvement recited in claim 3 wherein saidsecond energy-absorbing means comprises a portion of said lower memberconstructed in annularly corrugated manner to be subject toaccordionlike radial expansion and axial shortening under said forces,said abutment means being adapted to connect said upper member directlywith said lower member.
 6. The improvement recited in claim 3 whereinsaid second energy-absorbing means comprises a second set of spacedannular rows of deformer rolling bodies interposed with interference fitbetween said lower member and a further member received over said lowermember, said abutment means being adapted to connect said upper memberwith said further member for conjoint telescoping movement thereofrelative to said lower member following said first stage of movement. 7.The improvement recited in claim 1 further including one-way releasablebracket means fixed to said upper member and adapted for attachmentwithin the vehicle in a manner permitting said downward telescopingmovement thereof but preventing upward movement thereof, at least one ofsaid energy-absorbing means being operative for controlled resistance toupward movement of said lower member against the reaction provided bysaid bracket means.
 8. An energy absorber comprising first tube means,second tube means telescopically related with said first tube means, atleast one annular row of deformer rolling bodies interposed withinterference fit between said first and second tube means and operativeto roll thereover during an initial stage of telescoping movementbetween said tube means in one direction to effect predetermined plasticstrain grooving therein during such movement providing a first level ofenergy absorption, third tube means telescopically related with saidsecond tube means, at least one annular row of deformer rolling bodiesinterposed with interference fit between said second and third tubemeans operative to roll thereover during telescoping movementtherebetween to effect predetermined plastic strain grooving therein,and abutment means on said first and said third tube means engageablefollowing completion of said first stage of telescoping movement of saidfirst tube means to connect said first and third tube means for conjointtelescoping movement relative to said second tube means and conjointrolling of the first and the last mentioned rows of deformer bodies sothat continued telescoping movement of said first tube means in said onedirection occurs with a second level of energy absorption effected byboth said first and last mentioned rows of deformer bodies.
 9. Inenergy-absorbing steering column apparatus for automotive vehicles andincluding a telescopic steering shaft adapted for operative connectionbetween the steering gear of the vehicle and a manual steeringinstrumentality, and a support jacket mountable on the vehicle androtatably supporting said shaft, the improvement comprising, said jacketbeing constructed of telescopically related upper and lower tubes, theupper of said tubes being adapted to telescope relative to the lowerthereof upon forces being applied to said instrumentality downwardlytoward said lower tube, one-way releasable bracket means fixed to saidupper tube and adapted to permit said downward telescoping movementthereof but prevent upward movement thereof, at least two axially spacedannular rows of deformer balls interposed with interference fit betweensaid tubes and operative to roll thereover during an initial stage ofsaid downward telescoping movement of said upper tube to effectpredetermined plastic strain grooving in said tubes providing a firstlevel of controlled resistance to such telescoping movement, a thirdtube received telescopically over said lower tube below said upper tube,at least two axially spaced annular rows of deformer balls interposedwith interference fit between said lower and third tubes operative toroll thereover during telescoping movement therebetween to effectpredetermined plastic strain grooving therein, and abutment flangesmeans on said upper and said third tubes engageable upon completion ofsaid first stage of downward telescoping movement of said upper tube toconnect said upper and third tubes for conjoint telescoping movementdownwardly relative to said second tube such that both the first and thelast mentioned spaced rows of deformer balls are responsive to suchcontinued downward telescoping movement to provide a second higher levelof controlled resistance to such movement.